Method of making a monitoring pattern to measure a depth and a profile of a shallow trench isolation

ABSTRACT

A method of making a monitoring pattern to measure a depth and profile of a shallow trench isolation is disclosed. An example method of making a monitoring pattern of a shallow trench isolation profile forms a first pattern on a substrate to monitor a depth of a first shallow trench isolation. In the example method, the first pattern includes a plurality of unequally spaced active regions on the substrate. The example method also forms a second pattern on the substrate to measure electrical effects associated with a depth and a profile of a second shallow trench isolation. In the example method, the second pattern includes a plurality of equally spaced active regions on the substrate and a plurality of contact regions that electrically connect the equally spaced active regions.

FIELD OF THE DISCLOSURE

[0001] The present disclosure relates generally to semiconductor devicesand, more particularly, to a method of making a monitoring pattern tomeasure a depth and a profile of a shallow trench isolation.

BACKGROUND

[0002] There are two traditional methods for making monitoring patterns.One method is based on the well known in-line monitoring pattern and theother method is based on the well known unit device monitoring pattern.Both of these known methods are generally used to confirm criticaldimensions (hereinafter referred to as “CD”) and depth.

[0003] In a method for in-line monitoring pattern, as described inKorean Patent Registration No. 0301040, electronic beams are applied toa semiconductor substrate having an open pad composed of animpurities-doped poly-silicon layer formed in an in-line during thefabrication of semiconductor device. In response to the application ofthe electronic beams, the secondary electrons emitted from the pad areimaged as black or white.

[0004] A conventional method for measuring the depth of shallow trenchisolation (STI) is disclosed in Korean Patent Publication No.2001-0066143. A trench and an insulating layer respectively having alength of 0.4 micrometer are alternately provided to form a pattern inthe shape of a lattice. An indicating value of nanospec is set accordingto a depth of the trench, which is detected in a constant frequency bandcorresponding to a thickness of the insulating layer. Then, a laser beamis scanned on the pattern in the shape of a lattice using a nanospecdevice to detect the indicated value in the desired frequency band.Then, the indicated value is calculated in terms of a thickness.

[0005] Another method for forming patterns for measuring an STI profileis disclosed in Korean Patent Registration No. 0316054. With thismethod, a test pattern is formed that has many bar patterns with regularwidth to form an isolation layer of a device to define an active region.A process is then monitored by measuring the degree of protrusion orsinking of the isolation layer of the device via detecting thedifference between the width of the active region and the width of theisolation layer of the device by using Atomic Force Microscope (AFM)equipment.

[0006] Further, U.S. Pat. No. 6,350,994 discloses a structure of CD bar.The CD bar is formed on a substrate between dies. A base layer is formedon a portion of the substrate. A critical material layer is then formedon the die, the base layer and the substrate with a uniform thickness.The base layer has a thickness that provides a surface profile the sameas the die. A die photomask pattern and first and a second testphotomask patterns on a photomask are then transferred to the criticalmaterial on dies, the base layer, and the substrate, respectively. Thesethree photomask patterns have the same pattern width.

[0007] Still further, U.S. Pat. No. 4,364,010 discloses a semiconductordevice with a monitor pattern and a method for monitoring deviceparameters. The monitor pattern comprises a semiconductor layer, a firstregion, a second region, and a third region. The first region is formedin the semiconductor layer. The second region is formed within the firstregion so that the surface of the first region is divided into twoportions. The third region is formed in the semiconductor layer andelectrically connected to the substrate. One of the two portions of thefirst region is electrically connected to the third region. As thesecond region becomes deeper, the connection (lying beneath the secondregion) that connects the two portions of the first region becomesthinner. As this connection becomes thinner, its resistance isincreased. Thus, monitoring of resistance between the two portions ofthe first region provides an index of the depth of the second region,and thereby doping profile changes during manufacture.

[0008] With the conventional methods described above, it is possible tomeasure CD and depth and forming a monitoring pattern of a unit devicesuch as a transistor and a diode. However, there remains a difficulty informing a monitoring pattern of composite devices.

[0009] As the technology of fabricating semiconductor develops, chipsizes decrease, the line width of circuits becomes thinner, andcomposite devices become more prevalent. Therefore, known methods ofusing an in-line monitoring pattern and unit device monitoring patternwill soon reach their technological limits.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 illustrates an example pattern for monitoring the effectson devices according to the depth and profile of shallow trenchisolation.

DETAILED DESCRIPTION

[0011] As described in greater detail herein, a monitoring pattern of ashallow trench isolation (STI) profile measures the effects on a deviceaccording to the depth and profile of STI by forming a pattern for theSTI profile and a pattern for monitoring the depth of the STI.

[0012] In particular, an example method of making a monitoring patternof an STI profile to confirm the effects on devices according to thedepth and profile of the STI forms a first pattern for monitoring thedepth of the STI. The first pattern has a plurality of active regionswith unequal spacing on the substrate. A second pattern is formed tomeasure electrical effects by the depth and profile of the STI. Thesecond pattern has a plurality of active regions on the substrate and aplurality of contact regions for electrical interconnections between theequally spaced active regions.

[0013] In general, the examples described herein relate to a monitoringpattern of an STI profile and to a method for forming a pattern whichcan monitor very small differences between the depths of the trenchinsulating layers in an STI structure. With conventional technology, STIprofile monitoring is typically performed for patterns of about 100 μm.However, due to the proliferation of more highly integrated devices andthe fact that post-processes and electrical effects on devices can beadversely affected by finer STI profiles, the methods disclosed hereinmay be particularly useful in alleviating these adverse affects.

[0014] A typical STI insulating layer relates to an oxide layer that isformed by the following processes. First, a trench is formed to separateactive regions on the semiconductor substrate. Second, the inside of thetrench is filled with a gap filling oxide layer. Then, etching andplanarization processes are performed. A significant difference betweenthe depths of the insulating layers in the STI structure causes severalproblems. If the insulating layer is substantially higher than thesurface of the active region, a spacer of a word line formed in the edgeof the insulating layer when the next word line is defined may result ina short between the word lines.

[0015] On the other hand, if the insulating layer is substantially lowerthan the surface of the active region, a large area of the side surfaceof the active region may be exposed. The exposed area forms a parasitictransistor, lowers the threshold voltage, increases the leakage current,and generally degrades the performance characteristics of thesemiconductor device.

[0016] Consequently, it is desirable to control precisely thethicknesses of the insulating layers on the active region. It is acritical factor in improving the yield of a device to monitor preciselythe heights of the insulating layers compared with those of the activeregions.

[0017]FIG. 1 illustrates an example pattern for monitoring the effectson devices according to the depth and profile of a STI. The examplemonitoring pattern of an STI profile described herein is divided intotwo parts: a pattern for monitoring depth of a STI 50 and a pattern formeasuring electrical effects on a semiconductor device by the depth andprofile of a STI 60.

[0018] First, for the pattern for monitoring the depth of the STI 50,non-trench-etched active regions 10 are formed. The space between theactive regions in the pattern for monitoring depth after the STI 50 isformed with unequal spacing to monitor precisely while sampling apattern for measuring electrical effects by the depth and profile of theSTI 60. Next, the pattern for measuring electrical effects by the depthand profile of the STI 60 is formed as described below. First, aplurality of non-trench-etched active regions 11 is formed. The spacingbetween the active regions 11 is preferably equal. Second, trench-etchedregions 30 are formed. Third, a plurality of contact regions forelectrical interconnections between the active regions 11 is formed.Finally, a plurality of gates for the transistor generation is formed.

[0019] An example monitoring pattern of an STI profile may be embodiedas depicted in the example structure of FIG. 1. With this monitoringpattern, the depth and profile of STI may be monitored and the effectson a device after STI etching according to density and size of thepattern may be determined. In addition, the depth and profile of STI canbe monitored in a single monitoring pattern and the STI profile can bemonitored by measuring the width and depth of slope with a SEM (ScanningElectron Microscope).

[0020] Thus, the example monitoring pattern of STI profile describedherein is generally divided into two parts: a pattern for monitoring thedepth of the STI 50 and a pattern for measuring electrical effects bythe depth and profile of the STI 60. With this monitoring pattern, depthand profile of STI may be monitored and the effects on a device may bedetermined. Those having ordinary skill in the art will readilyappreciated that the examples described herein may be advantageouslyapplied in semiconductor device fault analysis and research anddevelopment of semiconductor devices.

[0021] Although certain methods and apparatus have been describedherein, the scope of coverage of this patent is not limited thereto. Tothe contrary, this patent covers all embodiments fairly falling withinthe scope of the appended claims either literally or under the doctrineof equivalents.

What is claimed is:
 1. A method of making a monitoring pattern of ashallow trench isolation profile, comprising: forming a first pattern ona substrate to monitor a depth of a first shallow trench isolation, andwherein the first pattern includes a plurality of unequally spacedactive regions on the substrate; and forming a second pattern on thesubstrate to measure electrical effects associated with a depth and aprofile of a second shallow trench isolation, wherein the second patternincludes a plurality of equally spaced active regions on the substrateand a plurality of contact regions that electrically connect the equallyspaced active regions.
 2. The method as defined by claim 1, wherein thedepth, the profile and the electrical effects are monitored according todensity and size of the first and second patterns.
 3. The method asdefined by claim 1, wherein the depth and the profile are monitoredusing a single monitoring pattern.